Fever may occur in the late stage of lung cancer. There are two reasons for fever in the late stage of lung cancer: 1. Tumor of lung cancer itself can lead to fever. But the fever caused by tumor is low fever, the fever potential is not high, within 38.5℃, accompanied by obvious night sweating or wasting. 2. Lung cancer combined with obstructive pneumonia and secondary bacterial infection, at this time, the patient has chills, fever, cough and yellow sputum. Therefore, fever may occur in the advanced stage of lung cancer, but one of the reasons for fever is the tumor itself, and the other is secondary infection, which needs careful clinical differentiation.